Instance Variables - EduardoMSU/OOP-2143 GitHub Wiki

Instance Variables in Object-Oriented Programming (OOP)

What are Instance Variables?

Instance variables are variables that are associated with a particular object (instance) of a class. Each object has its own copy of the instance variables, which hold the state or data unique to that object. Instance variables are typically declared inside a class but outside of any method, constructor, or destructor.

Key Characteristics of Instance Variables

Characteristic Description
Object-Specific Each object has its own set of instance variables, meaning each object can have different values.
State Representation Instance variables typically represent the state of an object (e.g., attributes like color, size, etc.).
Declared Inside Classes They are declared inside the class definition, but outside any methods, constructors, or destructors.
Access Modifiers Instance variables can have access modifiers like private, protected, or public to control access.
Lifetime Instance variables exist as long as the object exists and are destroyed when the object is destroyed.

Syntax for Instance Variables in C++

Example of a Class with Instance Variables

#include <iostream>
using namespace std;

// Class definition
class Car {
public:
    // Instance variables (attributes)
    string make;
    string model;
    int year;

    // Constructor
    Car(string m, string mo, int y) {
        make = m;
        model = mo;
        year = y;
    }

    // Method to display the car details
    void displayDetails() {
        cout << "Car Make: " << make << ", Model: " << model << ", Year: " << year << endl;
    }
};

int main() {
    // Create an object of class Car
    Car car1("Toyota", "Corolla", 2020);
    
    // Accessing instance variables and methods
    car1.displayDetails();  // Car Make: Toyota, Model: Corolla, Year: 2020

    return 0;
}
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